We will complete our last heat flow transect sometime in the wee hours of the morning. Because I forgot to explain out the process works…here it goes:
We deploy ANGUS (pictures to come) from the fantail of the ship. This is a VERY heavy instrument, which includes a data logger, battery and 11 thermistors that is lowered into the water by a winch on the ship. Once the probe is settled ~100-200m above the ocean floor. We know the depth of the ocean floor from one of the many screens that collects data in the computer lab. When ready, we “send the probe into the mud” at 60 meters/minute. We watch a few of the screens to determine when ANGUS has penetrated the sediments (mud) on the ocean floor, which is identified by a frictional heating of the thermistors. At this point the thermistors will separate (we can see 3 of them on the computer screens). During this time the thermistors collect temperature information from the seafloor. After 7 minutes a heat pulse fires, which is used to collect information about the thermal conductivity of sediments on the seafloor. After another 7 minutes the winch will slowly pull the probe out of the mud. Once it is completely out, ANGUS is pulled to ~100-200m above the seafloor, and we head to the next point on the transect, until the last point when we recover the instrument onto the deck.
A total of 17 transects have been completed during our month at sea. Many transects were across the deformation front, while the other were taken over interesting features that were illuminated during our seismic surveys. Recovery the ANGUS onto the fantail proved to be quit challenging in 4-6 meter swells. There were many times that it appeared like the ocean would devour us, luckily that never happened. The probe will be recovered one more time before we transit to port in Napier. I am grateful (and thankful) for my watch partner – Dylan Baker. Must have been fate seeing his last name is the same as my youngest furbaby.